Consolidated Statement of Stockholders' Equity and Comprehensive Income (Loss) (USD $) In Thousands | Total | Class A Common Stock | Class B Common Stock | Treasury Stock | Paid-in-Capital | Retained Earnings | Accumulated Other Comprehensive Income/(Loss) | Comprehensive Income |
|---|
| Balance at Dec. 31, 2009 | $ 534,234 | $ 60 | $ 28 | $ (2,474) | $ 448,556 | $ 95,263 | $ (7,199) | |
| Balance (in shares) at Dec. 31, 2009 | | 59,170 | 28,169 | | | | | |
| Comprehensive income (loss): | | | | | | | | |
| Net income | 77,741 | | | | | 77,741 | | 77,741 |
| Unrealized gain on derivatives designated and qualified as cash flow hedges, net of tax of $2,718 and $1,367 for the nine months ended on September 30, 2011 and 2010, respectively | 2,389 | | | | | | 2,389 | 2,389 |
| Foreign currency translation adjustments | 501 | | | | | | 501 | 501 |
| Comprehensive income | 80,631 | | | | | | | 80,631 |
| Issuance of common stock | 201 | | | 197 | 4 | | | |
| Issuance of common stock (in shares) | | 29 | | | | | | |
| Purchase of treasury stock | 0 | | | 0 | | | | |
| Purchase of treasury stock (in shares) | | | | 0 | | | | |
| Preferred stock dividends | (15,261) | | | | | (15,261) | | |
| Non-cash stock-based compensation | 2,376 | | | | 2,376 | | | |
| Balance at Sep. 30, 2010 | 602,181 | 60 | 28 | (2,277) | 450,936 | 157,743 | (4,309) | |
| Balance (in shares) at Sep. 30, 2010 | | 59,199 | 28,169 | | | | | |
| Balance at Dec. 31, 2010 | 619,483 | 60 | 28 | (2,277) | 451,728 | 171,224 | (1,280) | |
| Balance (in shares) at Dec. 31, 2010 | | 59,199 | 28,169 | | | | | |
| Comprehensive income (loss): | | | | | | | | |
| Net income | 94,590 | | | | | 94,590 | | 94,590 |
| Unrealized gain on derivatives designated and qualified as cash flow hedges, net of tax of $2,718 and $1,367 for the nine months ended on September 30, 2011 and 2010, respectively | 4,751 | | | | | | 4,751 | 4,751 |
| Foreign currency translation adjustments | (1,277) | | | | | | (1,277) | (1,277) |
| Comprehensive income | 98,064 | | | | | | | 98,064 |
| Issuance of common stock | 237,253 | 16 | | | 237,237 | | | |
| Issuance of common stock (in shares) | | 16,000 | | | | | | |
| Conversion of stock | | 14 | (14) | | | | | |
| Conversion of stock (in shares) | | 14,387 | (14,387) | | | | | |
| Preferred stock dividends | (4,726) | | | | | (4,726) | | |
| Exercise of stock options | 18,621 | 1 | | | 18,620 | | | |
| Exercise of stock options (in shares) | | 1,572 | | | | | | |
| Non-cash stock-based compensation | 2,895 | | | | 2,895 | | | |
| Balance at Sep. 30, 2011 | $ 971,590 | $ 91 | $ 14 | $ (2,277) | $ 710,480 | $ 261,088 | $ 2,194 | |
| Balance (in shares) at Sep. 30, 2011 | | 91,158 | 13,782 | | | | | |