Earnings Per Share (Basic and Diluted Earnings (Loss) Per Common Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share [Abstract]
Net income attributable to common stockholders - Basic																	$ 53,603	$ 36,178		$ 49,791
Impact of assumed conversions:
Interest on convertible notes																	0	0		1,959
Net income attributable to common stockholders - Diluted																	$ 53,603	$ 36,178		$ 51,750
Weighted average common shares outstanding - Basic																	54,511	51,346		48,185
Assumed conversions:
Incremental common shares from warrants																	121	1,355		1,560
Incremental common shares from stock options																	880	1,133		992
Incremental common shares from restricted stock units																	14	7		116
Incremental common shares from convertible senior notes																	0	0		2,701
Weighted average common shares outstanding - Diluted																	55,526	53,841		53,554
Basic earnings per common share (in dollars per share)	$ 0.30	[1]	$ 0.26	[1]	$ 0.20	[1]	$ 0.22	[1]	$ 0.21	[1]	$ 0.17	[1]	$ 0.17	[1]	$ 0.16	[1]	$ 0.98	$ 0.70	[1]	$ 1.03
Diluted earnings per common share (in dollars per share)	$ 0.29	[1]	$ 0.26	[1]	$ 0.20	[1]	$ 0.22	[1]	$ 0.20	[1]	$ 0.16	[1]	$ 0.16	[1]	$ 0.15	[1]	$ 0.97	$ 0.67	[1]	$ 0.97

[1] The sum of the quarterly earnings per share (basic and diluted) may not agree to the earnings per share for the year due to the timing of common stock issuances.